The limiting strength of conventional hinged or jointed structures utilizing sheet or panel members of low unit strength to form the structure is the ability of such members to carry localized stresses at points of attachment. There has accordingly existed for some time a need for better means of joining the edges of materials having relatively low resistance to localized loading stresses, such as that imposed by rivets, screws, spot welding and the like. Sheet or panel materials which give rise to the problem include formed plastic sheet, foamed core/stressed skin laminates, corrugated board, chipboard, felt laminates and similar light weight, low cost but easily rupturable stock commonly used in fabricating containers or other vessels, display structures, protective pads, folio covers, etc.
Various tape constructions for joining mating edges of such materials have been advanced heretofore. A common arrangement is illustrated in U.S. Pat. Nos. 589,504, 1,260,197, 1,833,469 and 3,035,752 where the junction is formed by fabric or paper strips or tabs which are simply glued to the faces of the members to be joined. One particular difficulty with these arrangements is their poor resistance to peeling of the tabs from the faces of the joined members when forces are applied tending to move the members bodily relative to each other. Another form is illustrated in U.S. Pat. Nos. Re. 18,204, 1,988,036, 2,025,926, 3,442,415, and French Pat. No. 1,099,154 published Aug. 31, 1955. This form of joint-forming tape is characterized generally by the employment of two coextending tapes which are stitched together along their center lines to form an X-like configuration in cross section. The legs of the X are then glued or otherwise secured to the margins of the members to be joined. This represents an improvement over flat tape but the stitching, falling as it must at the axis of the hinge, weakens the structure at its most critical location.
Still another approach used for hingedly joining members is represented by the constructions shown in U.S. Pat. Nos. 46,071, 570,365 and 2,219,524. The arrangements there shown are not longitudinally continuous of the joined edges, so that a plurality of separate hinges must be used; and their attachment to the members to be joined presents problems. Molded plastic hinges of the type illustrated in U.S. Pat. Nos. 3,202,310 and 3,301,430 are designed to provide a continuous joint along the mating edges, but here again a problem is encountered in providing suitable means for securing such joint-forming constructions to the panel members.
Joint forming tapes of woven construction are disclosed in U.S. Pat. Nos. 2,200,882, 2,245,095, 3,374,793, in French Pat. No. 1,099,154 mentioned above, and in Britich Pat. No. 970,771 published Sept. 23, 1964. All of these arrangements relate to garment use, the first four being designed to join elasticized panels in a foundation garment and the fifth being designed to support zipper elements to permit them to be sewn into a garment. As will appear more fully later, none of these arrangements is capable of use for joining rigid panel members to provide a freely articulatable structure in which the articulated members are nevertheless constrained to hinge about a single definite axis.
Other prior art includes U.S. Pat. No. 2,766,504 for fabric binding or trimmings: U.S. Pat. No. 3,618,754 for a conformable elastic adhesive tape; and U.S. Pat. Nos. 2,949,264 and 3,294,605 both relating to joints in inflatable fabric structures. Again however these do not disclose a tape capable of forming a definite hinge axis between panel members joined by the structures described.